Method of manufacturing glass substrate for magnetic recording media

Abstract

The invention provides a method of manufacturing a glass substrate for magnetic recording media. And the glass substrate has high surface smoothness and little waviness. In the primary, secondary and tertiary lapping process, diamond pads 20 A, 20 B, and 20 C are used, respectively. The diamond pad 20 A has an average diamond grain size of 4 to 12 μm, and a content of diamond grains of 5 to 70% by volume. The diamond pad 20 B has an average diamond grain size of 1 to 5 μm, and a content of diamond grains of 5 to 80% by volume. The diamond pad 20 C has an average diamond grain size of 0.2 to 2 μm, and a content of diamond grains of 5 to 80% by volume. In the polishing process, the silicon oxide is used as abrasive without using cerium oxide.

What is claimed is: 
     
         1 . A method of manufacturing a glass substrate for magnetic recording media, comprising:
 a primary lapping process,   a secondary lapping process,   a tertiary lapping process, and   a polishing process, for a surface except for an end face of a glass substrate,   in this order;   in the primary, secondary and tertiary lapping process, a diamond pad on which diamond abrasive grain was fixed using binder was used, and the surface of the diamond pad has a structure in which plural tile-like projections having a flat top were provided in line;   wherein   the diamond pad used in the primary lapping process has an average diamond grain size of 4 to 12 μm, and a content of diamond grains in the projection of 5 to 70% by volume,   the diamond pad used in the secondary lapping process has an average diamond grain size of 1 to 5 μm, and a content of diamond grains in the projection of 5 to 80% by volume,   the diamond pad used in the tertiary lapping process has an average diamond grain size of 0.2 to 2 μm, and a content of diamond grains in the projection of 5 to 80% by volume, and   in the polishing process, silicon oxide is used as abrasive.   
     
     
         2 . The method of manufacturing a glass substrate for magnetic recording media according to  claim 1 ,
 wherein the size of the projections of the diamond pad used in primary, secondary and tertiary lapping process, is 1.5 to 5 mm square with a height 0.2 to 3 mm, and the space between adjacent projections is 0.5 to 3 mm.   
     
     
         3 . A method of manufacturing a glass substrate for magnetic recording media, comprising:
 a primary lapping process,   a secondary lapping process, and   a polishing process, for a surface except end face of a glass substrate,   in this order;   in the primary and secondary lapping process, the diamond pad on which diamond abrasive grain was fixed using binder is used, and the surface of the diamond pad has a structure in which plural tile-like projections having a flat top were provided in line;   wherein   the diamond pad used in the primary lapping process has an average diamond grain size of 3 to 12 and a content of diamond grains in the projection of 5 to 70% by volume,   the diamond pad used in the secondary lapping process has an average diamond grain size of 0.2 to 5 μm, and a content of diamond grains in the projection of 5 to 80% by volume, and   in the polishing process, the silicon oxide is used as abrasive.   
     
     
         4 . The method of manufacturing a glass substrate for magnetic recording media according to  claim 3 ,
 wherein the size of the projections of the diamond pad used in primary, secondary and tertiary lapping process, is 1.5 to 5 mm square with a height 0.2 to 3 mm, and the space between adjacent projections is 0.5 to 3 mm.   
     
     
         5 . The method of manufacturing a glass substrate for magnetic recording media according to  claim 1 , wherein in the polishing process, silicon oxide is used as abrasive without using cerium oxide. 
     
     
         6 . The method of manufacturing a glass substrate for magnetic recording media according to  claim 2 , wherein in the polishing process, silicon oxide is used as abrasive without using cerium oxide. 
     
     
         7 . The method of manufacturing a glass substrate for magnetic recording media according to  claim 3 , wherein in the polishing process, silicon oxide is used as abrasive without using cerium oxide. 
     
     
         8 . The method of manufacturing a glass substrate for magnetic recording media according to  claim 4 , wherein in the polishing process, silicon oxide is used as abrasive without using cerium oxide.